Automatic telephone system



Feb..4, 1930. M'. 'LANGER AUTOMATIC TELEPHONE SYSTEM Filed April 22,'1927 3 sheds-sheet Rm g Feb. 4, 1930. M. LANGER AUTOMATIC TELEPHONESYSTEM Filed April 22, 1927 -'Imranar- Wax Lan er' HTH.'

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s sneaks-sheet 5 Filed April 22, 1927 w N Nk w@ .was kk Patented Fei. 4,1930 AUNrrlszD STATES PATNT '.oFFlc-E MAX LANGER, OF BERLIN, GERMANY,ASSIGNOR T0 SIEMENS 8c HALSKE AKTIEN- GESELLSCHAFT, WERNERWERK, O FSIEMENSSTAD'I,jIEIVEAIEI.- BERLIN, GERMANY i' AUTOMATIC TELEHON E SYSTEMApplication led vApril 22, 1927, Serial No. 185,806, and in Germany May12, 1926.

' The present invention relates to automatic telephone systems ingeneral, and more particularly to the setting up of calls of differentvalue in systems comprising main and sub-exchanges.

In such systems,iit is known to locate in the main exchange a portion ofthe connection devices to be used bythe sub-exchanges, and to take intouse for setting-up each call a junction line from the sub-exchange goingto the.main exchange. In that case when a call is made to a stationbelonging to the calling sub-exchange, a devicer (such as an auxiliaryswitch) associated with the' junction line taken into use then freesthis junction line and the connecting-device taken into use at the mainexchange, and the connectionis switched over to the connecting devicesat the sub-exchange. If high value calls (for example from atrunk-position of the main exchange) are made toa sub-exchange and thejunction lines be connected in the sub-exchange in the same manner assubscribers lines, a junction line to the main exchange has to be takeninto use likewise for these calls in the known arrangements, and therelease of the seized junction line and the switching over to theconnecting devices of this sub-exchange cannot take place until thissub-exchange has been designated.

Now/the 'ob`ect' of the invention is to obvi- Aate lthe needless takinginto use 'of a junction to the main exchange in that case, thisbeingachieved by providing the connecting devices at'the sub-exchange and tobe used for all calls with switching means, which in different waysaiect the common connecting device according to the value of theconnection to be set up; hence when a low value call is initiated, thecalling line is connected to a junction line going to the main exchange,and when a high value call is initiated, the calling line is connectedto a junction line going to another connecting device at thesub-exchange. j

By way of example the drawings comprising Figures 1, 2, and 3, sho7 thedevices at a sub-exchange and the connecting devices to be used incommon for the high and low value calls. In this example the incomingunction lines (trunk lines) are connected to the same I The drawingsshow two types of these pre# selecting devices. Thus in Figure l asubscribers station N land an incoming trunk line FL are connected tothe same call seeker AS,'while in Figure 3 a subscribers station N 2 isconnected to a preselector I.VW 1 and an incoming trunk line FL 2 isconnected to a preselector I VW 2. The Figure 2 sho'ws a iinal selectorLW of the sub-exchange,'which is suitable for setting up high and lowvalue calls. The call seeker AS shown in Figure 1 is connected to asecond preselector II.VW 1, over the bank contacts of which a group ofjunction lines going to the main exchange and to a group of finalselectors is reached.

The preselectors LVW 1 and LVW 2 (Figure 3) belonging respectively to asubscribers station and a trunk line have common means of .access tosecond preselectors, of the latter the Figure 3 shows the preselectorILVW 2.

The method of operating the arrangement shown in the Figures 1 and 2will rst be described. For this purpose it will be assumed that thesubscribers station N 1 wishes to set up a call to another subscribersstation of the sub-exchange.

When the subscriber N 1 takes down his receiver, the winding I of thecalling relay T is energized in series with the winding of the startingrelay An common to a group of subscribers', the circuit extending overthe back contacts 1 t and 2 t. The relay T is so constructed that whenit is energized over the just described circuit, it only operates its'contact 3 t, while the contacts 1 t and 2 t remain closed. At itscontact 4 an the relay An closes the following circuit for the rotarymagnet DM 1 of the call seeker AS: earth, interrupter Un 1, contacts 4am, 5 p, rotary magnet DM 1, battery, earth. The wipers a, b, 0, and dof the call seeker AS are now operated step by step until the test wiperc reaches the bank contact 6 designated by the contact 3 t. The relay Pis then energized in the following circuit: earth, windings I and II ofP, wiper c, contacts and 3 t, winding II of the relay T, battery, earth.The relay P at its contact 5 p interrupts the circuit of the rotarymagnet DM 1 and at its contact 7 p it switches the starting circuitextending over the contact 4 amv over to the next idle call seeker ofthe same group. Atthe contact 8 p the high resistance winding I of thcrelay IJ is shortcircuited, and over the Contact 9 p the ,followingcircuit is closed for the second preselector ILVVV l connected to thecall seeker AS battery, contacts 9 p, 10 u,v winding of the rotarymagnet DM 2, contact 11 t 1, interrupter Un 1, earth. At the contact 12p a circuit for the change over relay U of the preselector ILVIV l, isclosed, which extends from earth over the winding I of this relay,contact 12 p, wiper d, winding of the register magnetl Z, contact 3 tand over the winding II of relay T to battery and earth. But in thiscircuit neither the relay U nor the register magnet Z can be operated inparallel with the low resistance winding II of the relay P.

Owing to the short circuiting of the highresistance winding I of therelay P, the relay T is fully energized over its winding II, hence itopens its contact 1 t and 2 t and thus disconnects the starting relayAn. Furthermore, the relay P at its contacts 13 p and 14 p connects theincoming speaking leads over the wipers a and b of the call seeker ASthrough to the speaking leads of the second preselector ILVW 1. In themeantime this preselector has been started up as above described and itis arrested when it reaches an idle junction line going to the mainexchange, at the outgoing end of which line there is an impulse andspeech current repeater.

Assuming that the repeater marked Uein the Figure 1 is free, thefollowing circuit for the test relay T 1 of ILVW 1 is established whenthe wiper c 1 reaches the test contact of this repeater: battery,windings I and II of T 1, contact 15 u, wiper c 1, contact 16 s, windingI of relay 1, contact 17 'u 1, earth. In this circuit the relays T 1 andC 1 are energized. The relay T 1 at its contact 11 t 1 interrupts thecircuit of the rotary magnet DM 2, at its contact 18 t 1 it shortcircuits its high resistance winding II, and at its contacts 19 t 1 and20 t 1 it connects the call through over the wipers a 1 and b 1 to thespeaking leads of the repeater Ue taken into use. Thereat the relays Aand B are energized over the subscribers loop. The relay C 1, which wasenergized when the repeater was taken into use, closes the followinglocking circuit over its winding II; battery, contacts 21 s and 22 c l,winding II of relay C 1, contact 23 a,

-.-winding of relay V l, earth. The relayV 1 is likewise energized overthis locking circuit, and at contact 17 'v l it opens the circuit forthe winding I of the relay C 1 and by closing its contact 24 e 1 itmaintains the marking engaged circuit for the relay T 1 of the secondpreselector II. V W 1 over the resistance WV.

Inadditon to the repeater Ue, the outgoing end of each junction linegoing to the main exchange is provided with an auxiliary switch MS,which in known manner releases the junction line going to the mainexchange when a local call is made. On operating, the relay V 1 at itscontact 25 'v 1 closes the following circuit for the rotary magnet DS ofthe auxiliary switch MS: earth, contacts 25 v 1 and 26 v 2, wiper 27 ofMS, winding of the rotary magnet DS, battery, earth. The wiper 27 of theauxiliary switch MS is moved on one step, whereupon the rotary magnet DSis placed under the control of the impulse receiving relay A.

If the rst train of impulses now be transmitted by the callingsubscribers station N 1, the relay A falls back at each impulse, and atits contact 28 a it closes the following circuit for the rotary magnetDS of the auxiliary switch MS: earth, contacts 25 v 1, 29 g, 28 a,winding of DS, battery, earth. At the same time at each impulse theopening of contacts 23 a removes the short circuit from the winding ofthe relay V 2 and in place thereof the contacts 30 a close and shortcircuit the winding II of the relay C 1. The latter is, however, a slowacting relay and therefore does not fall back during the individualimpulses. At the end of each impulse the winding of relay V 2 is againshort-circuited at contacts 23 a, but as it is thereby rendered slowacting, the relay maintains its contacts in the operated position forthe duration of the train of impulses. At contact 31 @,the impulses re-`ceived by the relay A are repeated over the contact 32 c 1 and over thelead La to the switch located at the incoming end of the junction lineat the main exchange, while at the contacts 34 o 1 and 35 v 2 thesteering current is applied to the other lead Lb. If the first train ofimpulses consists of 3 impulses, the following circuit is closed at theend of this train of impulses over the wiper 27 of the auxiliary switchMS: earth, contacts 25 v l, 26 u 2, wiper 27, winding of relay UR,contact 36 c 1, battery, earth. The relay UR at its contacts 135 urcloses a locking circuit for itself and at its contacts 37 ur preparesthe circuit of the relay S, which effects the switching over to theconnecting devices of the local sub-exchange. If the next train ofimpulses likewise consists of 3 impulses, at the end thereof thefollowing circuit is closed for the relay S: battery, contact 38 g, 37u1', winding of relay S, wiper 27 contacts 26 v 2 and 25 v 1, earth. Therelay S is opera-ted, at its contact 16 s it opens the circuit of relayT l at IIVW 1 and at its contact 39 s it closes a circuit for thewinding I of the change over relay U over resistance W 1 and the wiper e1 of ILVW 1.' At the same time the contact 21l s opens the lockingcircuit of the winding II of relay C 1, which falls back after a littlewhile and in known manner returns to their normal position the devicesat the-repeater Ue and at the auxiliary switch MS.v The relay G has thefunction of preventing the switching over taking place at thepreselector ILVW 1 when two more trains of im- 5 pulses are transmitted,consisting, forexample, of 2 and 4 impulses, whereby the w1per 27 of MSis likewise positioned on the contact to which the relay S is connected.For two impulses position the wiper 27 onto the third contact, whereuponthe relay G is energized after the relay V 2 has fallen back. The relayG opens its contact 29 g thus opening the impulse circuit for the rotarymagnet DS.

When the relay U operates at the second preselector ILVW 1, the testrelay T 1 of this switch is` connected over the contact 40 u and overwinding II of relay U to the second test wiper d 1 of the preselector.The rotary magnet DM 2 is connected up over the contact 41 u and overthe low resistance winding I II of the relay U. The wipers a 1,'b 1, c1, d 1 and e 1 of the second preselector ILVW 1 are now moved on untilan idle succeeding switch has been found, for example the final selectorLW shown in the Figure 2. In that case the following circuit is closedwhen the wiper al 1 reaches the test contact, to which the finalselector LW is connected: battery, windings I and II- of relay T 1,contact 40 u, winding II of relay U, wiper d 1, lead 42 (Figures 1 and2), winding I of relay C 2, contact 43 1', offnormal contact 44 7c ofLIV, earth. At the preselector II.VW 1 the relay T 1 is operated, itscontact 11 t 1 interrupts the circuitl of the rotary magnet DM 2 and itscontacts 19 t l and 20 t 1 connect the subscribers station N 1 to thespeaking leads 45 and 46 going to the final selector LW.

Thereby the relay's A 1 and B 1 of the final selector LW are energizedover the line loop of the calling subscriber. The relay C 2 is energizedwhen the final selector LW is taken into use and its contact 47 c 2closes a locking circuit for its winding II and its contact 48 c 2operates the relay U 1 over the off-normal contact 49 lc. At the contact50 c 2 a circuit is closed for the relay E extending over the shaftcontact 51 w. The actuation of the relays U 1 and E prepares the finalselector LW for the reception of the first train of impulses, becausethe contacts 52 u 1 and 53 e are closed in the circuit of the liftingmagnet H. When the calling subscriber transmits the next train ofimpulses, the opening of the line loop at each impulse causes the relaysA 1 and B l to fall back. At contact 54 a 1 the following circuit forthe lifting magnet H is closed earth, contacts 60 50 c 2, 54 a 1, 53 e,52 u 1, winding of H, battery, earth. The wipers a 2, b '2, c 2 of thefinal selector LW are raised step by step by the lifting magnet H. Atthe first, step of the switch the offl -normal contact is opened 65hence the contact 44 7c opens the circuit for energizing the winding Iof the relay C 2 and the contact 49 opens the circuit for energizing thewinding I of the relay U 1 The relay 'C 2 is locked, however, over itscontact 47 c 2 and its winding I'I, while the slow actingrelay U 1 ismaintained energized pulse circuit over the contact 57 u1. Hence whenthe next train of impulses is trans,- mitted from the subscribersstation N 1 the rotary magnet D is energized at 'each impulse over thefollowing route: earth, contacts 50 c 2, 54 a 1, 53 e, 57 u 1, windingof D, battery, earth. The shaft contact 51 w is opened at the firstrotary step, thereby interrupting the circuit for energizing the relayE. But this remains energized for the duration of this train of impulsesover the off-normal contact 58 k and the contact'59 d of the rotarymagnet. It s iould also be mentioned that the relayR w s energized overthe contacts 60 c 2 and61 e, and at its contact 62 9 it prepares thetest circuit for the relay P 1. Shortly after the end of the last trainof impulses the relay E falls back and closes the following circuit forthe test relay P 1: earth, contacts 60 c 2, 63 e, 62 r, windings-I andII of P 1, contact 64 f, wiper c 2 of the final selector LW and over thewinding II of the calling relay T (not shown) belonging to the wantedsubscribers station. The relay P 1 at its contact 65 p 1 short circuitsits high resistance winding I and it closes its contact 66 p 1, 67 p 1and 68 p 1, thereby applying ringing current to the wanted subscribersline as follows: battery, source of ringing current RQ, contacts 7, 71y, 72 f, 67 p 1, wiper a 2, upper lead of the subscribers line, bell atthe subscribers station, lower lead of the subscribers line, wiper b 2,contacts 68 p 1, 73 y, earth. Shortly afterwards the relay R falls backand closes the following circuitfor the intermittent ringing: from thesource of ringing current RQ over contact 69 1,winding II of the relay U1, contact 74 1' .and over the ringing route previously decribed. Thecontact 69 1 is closed periodically in known manner by a ringing relay,for example every 10 seconds.

"hen the wanted subscriber answers the call, the relay U 1, which onlyresponds to direct current, is operated over the Contact 1 and the abovedescribed ringing circuit to earth at contact 73 y. The relay thencloses at its contact 76 u 1 a circuit for the winding I of relay Yextending over the contacts 77 p 1 and 78 c 2. At the same time theringing circuit is opened at the contact 71 y and at Contact 73 g/ thewindings II and III of the relay Y are energized in the followingcircuit battery, winding II of Y, contacts 131 y, 72 f, 67 p 1, wiper a2, subscribers loop, wiper b 2, contact 68 p 1, Winding III of Y, earth.At contact 79 y battery is applied to the lead 80, hence the metermagnet Z of the calling subscribers meter is energized over the wiper e1 of the preselector ILVV 1, contact 12 p, wiper al of the call seekerAS, bank contact 6 and wiper c of AS, winding II and Contact 8 p ofrelay P to earth.

At the end of the conversation when the receiver is hung up at thecalling subscribers station N 1, the relays A 1 and B 1 fallback. Thelocking winding II of the relay C 2 is short circuited at contact 81 a1, and the relay falls back after a little while. At contact 82 c 2 thefollowing circuit is closed for the rotary magnet D: earth, contacts 82c 2, 83 ic. 84 e, 57 u 1, winding of the rotary magnet D, battery,earth. At Contact 59 d is closeda circuit for the relay E extending overthe contact 58 s. This effects the interruption of the circuit of therotary magnet D at contact 84 e. The rotary magnet opens its contact 59d, whereupon the relay E falls back again, and at contact 84 e againcloses the circuit of the rotary magnet. The interaction between therotary magnet and the relay E continues until the wipers have been movedbeyond the row of bank contactson which they happen to be standing, theswitch shaft is then returned to the normal position. In the normalposition the contacts 83 c and 58 k are opened, hence the rotary magnetD cannot be again operated. At contact 60 c 2 is opened the circuitofthe test relay P 1, thus also causing the release of the relay Y. Atthe release of the relay C 2 the contact .Y

47 c 2 is opened and it removes earth from the lead 42, thus causing therelays T 1 and U to fall back at the preselector II.VW 1. Thereupon thesecond preselector ILVW 1 and the call seeker AS in known manner arereturned to the normal position.

The method of setting up a trunk call to a y subscriber of thesub-exchange will now be described. Upon initiating a call over thetrunk line FL shown in Figure 1, the relay T 2 is energized over itswinding I and over the contacts 85 t 2 and 86 t 2 in series with thestarting relay An. The relay T 2 closes its contact 87 t 2, therebyapplying battery over the winding II of this relay to the test contact88 of the' call seeker AS, while the contacts 85 t 2 and 86 t 2 remainclosed for the present. The call seeker AS is positioned in the mannerdescribed above. When the wipers a, b, c, and d of the vcall seeker havebeen positioned onto the bank contacts of the calling line, the WindingI of the relay U at the second preselector is energized over the wiperd, contact 12 p, winding I of relay U. At contact 40 a the test relay T1 is connected to the wiper d 1 of II.VW 1, over which only theconnecting devices of the local exchange can be tested. Hence the trunkcall is thus switched over to a iinal selector of the subexchangc assoon as the second preselector ILVWV '1 is taken into use.

The seizing of the inal selector LW and its positioning onto the wantedsubscribcrs line takes place in the manner described above for a lowvalue call, so it need not be further described.- However, upon therelease of the relay E at the end of the last train of impulses forpositioning the final selector the relay -F is energized in thefollowing circuit until the relay R falls back; earth, winding I of Il,contacts 89 e, 90 1', lead 80, wiper e 1 of ILVVV 1, contact 12 p, wiperd of AS, battery. The relay F at its contact 91 f closes over contacts134 5 1 and 135 t 3 a locking circuit over its winding II. At contact 647" the circuit of the test relay P 1 of the linal selector LW is opened,while at the contacts 92 f, 93 f and 94 f the speaking leads 45, 46 ofthe final selector LW are switched through over the condensers C 3 and C4 and over the wipers a 2 and b 2 of the final selector LW to the wantedstation. If the wanted subscribers station be engaged, the calling trunkoperator notifies him that he is wanted for a trunk call, and theoperator can then in known manner effect the release of the local call.It the receiver has been hung up in the meantime at the Wanted station,the relay B 1 is energized by the trunk operator and thus ringingcurrent is applied to the line of the wanted subscribers station. Atcontact 134 b 1 the short circuit is removed from the winding of relay T3, which is then operated. The contacts 96 t 3 and 97 t 3 bridge overthe condensers C 3 and C 4, the wanted line is marked engaged overcontact 95 t 3 and the contacts 132 t 3 and 135 t 3 are opened. Theringing current takes the following route: source of ringing current RQ,contacts 98 b 1, 93 f, 94 f and 96 t 3, wiper a 2, subscribers line,wiper b 2, contacts 97 t 3, 92 f and 73 y, earth. When the wantedsubscriber answers during a pause in the ringing, that is to say whenthe relay B 1 has fallen back, the relay Y is then operated over thecontacts 99 t 3, 136 b 1, 93 f, 94 f, 96 t 3, wiper a 2, subscribersline, wiper b 2, contacts 97 t 3, 92 f, and 73 y, earth. At the end ofthe conversation the connection is released in a manner similar to thatdescribed above for a low value call, so it need not be furtherdescribed. i

The second example shown in Fig. 3 will now be further described. Initthe subscribers lines and the trunk lines incoming from the mainexchange terminate at preselectors. When a call is originated by thesubscribers station N 2 belonging to the subexchange the relay R 1 isoperated, its windings I and II being connected to the subscribers loopover thg contacts 101 t 4 and 102 t 4. At contact 103 r 1 the followingcircuit is closed for the rotary magnet: battery,

contacts 103 1 1 and 104 t. 4, winding of the rotary magnet DM 3,interrupter U11l 2, earth. The wipers a 3, b 3, c 3, ,d 3 and e 3 of thepreselector I.VW 1 are now movedl on until an idle second preselector,for example, the preselector II.VW 2 shown in Figure 3, has been found.The following circuit is then established: battery, contact 105 1' 1,windings I and II of relay T 4, wiper c 3, winding I of relay R 2,contact 106 t 5, winding II of the relay R 2, earth. The relays T 4 andR 2 are energized in this' circuit. The relay T at its contact 104 t 4opens the circuit of the rotary magnet and at its contact 107 t 4 shortcircuits the high resistance winding I of the relay T 4. At the contacts101 t 4 and 102 t 4 the calling relay R 1 is disconnected from thesubscribers line and at the contacts 108 t 4 and 109 t 4 the line isswitched through to the wipers a 3 and b 3 of the first preselectorI.VW'1. Over the contact 110 t 4 battery is applied to the registermagnet Z 1, which is connected to the wiper e 3. However, thechange-over relay U 2 of the second preselector II.VW 2 cannot operatein series with the winding of the register magnet Z 1.

At contact 111 1' 2 the following circuit is closed for the rotarymagnet of the preselector II.VW 2: earth, interrupter Un 3, contacts 1111' 2 and 1-12 t 5, winding of the r0- tary magnet DM 4, battery, earth.At contact 113 1' 2 is prepared the test circuit of the secondpreselector II.VW 2. The wipers a 4, 5 4, o 4, a5 4 and e 4 are nowmoved on until an idle repeater, for example Ue 1, located at theoutgoing end of a junction line going to the main exchange has beenfound. There` upon the following test circuit is established: battery,wiper d 3 of I VW 1, Contact 107 t 4, winding II of relay T 4, wiper c3, winding I of relay R 2, contact 113 1' 2, windings I and II of relayT 5, contact 114 u 2, wiper c 4, contact 115 s 1 to earth. The relay T 5operated in this circuit opens at its contact 112 t 5 the circuit of therotary magnet DM 4, at contact 116 t 5 short circuits its highresistance winding I and at contacts 117 t 5 and 118 t 5 switchesthrough the calling subscribers line over the wipers a 4 and b 4 to therepeater Ue 1. Thereat the relays A 2 and B 2 are energized, whereuponthe impulse transmission from the calling subscribers station can -becommenced. If the first or the first and second train of impulsesdesignate the local exchange, the not shown auxiliary switch causes therelay S 1 to be operated in the manner already described with referenceto the Figure 1. The relay at its contact 119 s 1 energizes the windingI of the change over relay U 2 over the resistance W 3, while at contact115 s 1 is opened the circuit of the relay T 5. The relay U 2 isoperated and establishes the following circuit for the rotary magnet DM4 of the second preselector II.VW 2: earth, interrupter Un 3, windingIII of relay U 2, contacts 120 u 2, 112 t 5, windingvgf the rotarymagnet DM 4, battery, earth. Ahen the relay U 2 operates, it also closesthe contact 121 'zt-2 and thus connects its winding II to the wiper d 4.The rotar magnet now rotates the preselector II.V 2 until an idle finalselector has been found belonging to the sub-exchange, for example, theswitch 'LW 1 shown in the Figure 3. Thereupon the relay T 5 is energizedover the winding II of relay U 2, winding I of relay C 3 and over theoff-normal contact 122 lo of the final selector LW l. When the contacts117 t 5 .and 118 t 5 at the preselector II.VV 2 are then closed, therelays A 3 and B 3 of the final selector LW 1 are operated over thesubscribers loop. The final selector is positioned and the call iscompleted in the manner described above. When the wanted subscribersstation answers the call, the contact 123 y l is closed operating theregister magnet Z 1 of the calling subscribers station N 2 over thewipers e 4 of II.VV 2 and e 3 of LVW 1. `When the receiver is hung up atthe calling station, the winding II of relay C 3 is short circuited atthe contact 124 a 3 whereupon the relay C 3 falls back and at itscontact 125 c 3 opens the circuit of the relays U 2, T 5, R 2 and T 4.The preselectors I.VW'1 and II.VW 2 are then released in known manner.Should, however, a call be made over the trunk line FL 2, the relay R 3is operated and at its contact 126 1' 3 it closes a circuit for therotary magnet DM 5 of the rst preselector LVW 2, extending over thecontact-127 t 6 and over the interrupter Un 4. When an idle secondpreselector, for example, the preselector II.VW 2 has been found, therelay T 6 is operated over the following circuit: battery, contact 1281' 3, windings I and II of T 6, wiper c 5, winding I of relay R 2,contact 106 t 5, winding II of relay R 2, earth. The circuit of therotary magnet DM 5 is opened at contact 127 t 6 and winding I Iof relayT 6 is short circuited at contact 129 t 6. However, whena trunk line iscalling, the relay U 2 is energized as follows: battery, wiper d 5 ofLVW 2, contact 130 t 6, wiper e 5, winding I of relay U 2, earth. At itscontacts 114 u 2 and 121 u 2 the relay U 2 switches the test relay T 5of the second preselector II.VW 2 over from the wiper o 4 tothe wiper d4. The preselector II.VW 2 being now started up over contact 111 1' 2,only the final selector of the local sub-exchange can be tested over thewiper al 4. An idle nal selector such as LW 1 is taken into use andpositioned in the manner above described. But at the end of its rotarymovement the relay F 1 is energized over the wipers e 4 and e 5, contact130 t 6 and over the wiper d 5, and it effects the switching over fortrunk traffic at the final selector LW 1 in the manner described above.

What is claimed is:

1. In a telephone system, a finder, a selector connected to said finder,lines of two classes terminating in the banks of said finder, trunks oftwo classes accessibleJ in the banks of said selector, a switchassociated with each trunk of the first class, means for operating saidfinder to find the calling line when a call is initiated over any ofsaid lines, means for 'operating said selector to select an idle trunkof said first class when the calling line is of one class, meanscontrolled over the calling line ,for operating the switchassociated'with the selected trunk, means for causing said selector toselect an idle trunk of the second class when the switch associated withthe selector trunk of the first class is operated to a predeterminedextent, and means for operating said selector to select anidletrunkmeans controlled over the calling line for.

variably operating the switch associated with the selected trunk, meansfor causing said selector to release the selected trunk of the firstclass and select an idle trunk of the second class when the switchassociated with the selected trunk of the first class is operated 'to acertain extent, and means for operating said selector to select an idletrunk of the second class immediately when the calling line is of theother class. Y

3. In a telephone system, a selector switch, trunks of two classesaccessible to said switch, a discriminating switch associated with eachtrunk of the first class, two classes of calling lines, means forconnecting a calling line of either class to said selector, meansresponsive to said first means for operating said selector toautomatically select an idle trunk of the first class when the callingline is of one class, means controlled over the calling line forvariably operating the switch associated-with the selected trunk, meansfor causing said selector to release the selected trunk of the firstclass and select an idle trunk of the sec-- ond class when the switchassociated with the selected trunk of the rst class is operated to acertain extent, means for operating said selector to select an idletrunk of the second class immediately when the call# ing line is of theother class, a combination toll and local connector terminating eachtrunk of the second class, and means for causing the connectorterminating the selected trunk of the second class to operate as a localnected line is of a'particular class for causing the selector to selectan idle trunk of the non-corresponding class.

5. In a telephone system, a trunk hunting selector, a first and a secondclass of trunks accessible to said selector, a first and a second lineover which said selector may be controlled, means for causing saidselector to iind a trunk of the first class when the control thereof isexercised over said first line, and for causing said selector to find atrunk of the second class when the control of said selector is exercisedover said second line, and means controlled over said first line forcausing sai-d selector after it has found a trunk of the first class tocontinue hunting until it finds a trunkof the second class.

6. In a telephone system, a finder, a selector connected to said finder,subscribers lines and incoming interoflice trunks terminating in thebanks of said finder, outgoing interoiice trunks and local trunksaccessible in the banks of said selector, means for operating saidfinder to lind the calling subscribers line or the calling incominginteroiiice trunk when a call is `extended over any one of saidsubscribers lines or any one of said incoming interoiiice trunks, andmeans for operating said selector tohunt an idle one of said outgoinginteroliice trunks whenever said finder finds a calling subscribersline, and for operating said selector to hunt an idle one of said localtrunks whenever said finder finds a calling incoming interofce trunk.

7. In a telephone system, a trunk hunting switch for extending calls,two classes of trunks accessible to said switch, a test wiper fortesting one class of trunks, a test wiper for testing the other class oftrunks, means for starting the hunting operation of said switch when theswitch is taken for use to extend a call, a test relay and means forassociating it with either wiper depending .on the class of trunks overwhich the call is to be extended, and a circuit for energizing saidrelay to stop the hunting operation of saidl switch when it has found anidle trunk in the class of trunks tested, said circuit including thewiper with which the relay is associated.

8. In a telephone system, a switch having one hunting movement undercertain conditions and two hunting movements under certain otherconditions, a second switch accesv to said switch,vsubscribers lines,incoming w trunk llnes, means for extendlnv'a connectlon i 'v ".igzaaee'lsibleto saidrst switch, and means for caus- 5 ing said second switch'to operate in either of two distinct manners, the manner of operav tiondepending on whether theA seizure thereof bysaid rst switch followed onehunting movement or two hunting movements.

9, 'In a telephone system, a hunting switch, .a a plurality o trunks oftwo classes accessible from any of said lines to said switch, landvmeans responsive when a connectionis'exj tended for oprating saidswitch to automati L cally select an idle trunk of one class when l theconnectionis extended from a subscribers line andan idle trunk of theother class when `the connection is extended from a trunk line.

l0. In a telephone system, a line switch,

local'trunks and outgoing trunks accessible I to saidjswitch,subscribers lines andincoming trunks having accessto saidswitch, meansfor extending, a callfrom said lines or from said incomingtrunks to saidswitch, means responsive when a call isextended from a subscribers linefor operating' said switch to f automatically Select an idle one of saidoutn going trunks,` and means responsive when aV l call is extendedfrom'anincoming trunk' for operating said switch to automatically select 3oan idle 'one of said local trunks.

` In witness whereof, I hereunto 'subscribe my name this 1st day ofApril, A. D. l1927. y "l l MAX LANGER.

is j

